1. Field of the Invention
This invention relates to a device for measuring the number of pass persons who pass an area, and more particularly, an improved system employing the device for managing the number of entry persons who enter the area and exit persons who leave the area.
2. Discussion of the Related Art
There has been heretofore proposed a device for automatically measuring the number of persons who pass a gateway or passage without employing any ID cards, pass gates or the like, in which the passage (pass gate) is designed as a measuring area to allow the pass by persons one by one and a pair of or a plurality pairs of through-beam type sensors are arranged on both sides of the passage to detect in response to the interruption of the light beam whether or not a person has passed the passage. The number of the persons who passed the passage is measured by counting the number of the interruptions (pulses).
There also has been proposed a device, in which a sensor measuring distances is installed above an entrance to detect changes of the height of persons passing the entrance for counting the number of the persons.
In another conventional device, an image in a measuring area taken by a television camera is compared with the image on its former frame and a background to extract a moving object based on differences by such comparison. The device decides whether or not the extracted moving object has passed an entrance to measure the number of persons.
The foregoing conventional devices, however, have the disadvantages described hereinafter.
In the device employing the through-beam sensors, the separation when persons have entered abreast is not satisfactory. The device functions well only when there are a very small number of persons passing the passage, or may be applied to so designed pass gate where passengers are allowed to pass one by one, but it is not suitable for versatile use.
The conventional device employing the sensor measuring distances has the disadvantages that the sensor cannot be installed into the high ceiling and the measurable area is narrow because other area than a portion just below the sensor cannot be measured.
The conventional device employing the television camera to use differences between the image in the camera and the background/frame has the problems of a lowering of separation by a shadow and a lowering of separation by omission of a difference in the result. In the area other than the portion just under the camera, the accuracy of the separation is much lowered because of an overlap by the persons.
Thus, any conventional devices have the problem that they cannot accurately measure the number of persons with versatility.